<?php
header("Content-Type:text/html;charset=UTF-8");
$sz = array(
   array(
       "BCd" => 1212,
       "AvLEHgfkHF" => 1212,
   ),
    array(
        "BCADdsd" => 1212,
        "AeLEHDHgfkrtHF" => 1212,
    ),
);
function main(&$sz){
    $ke = key($sz);
    $sz[$ke]=array_change_key_case($sz[$ke],CASE_UPPER);
    $pd=next($sz);
    if(!$pd){
        return $sz;
    }else{
        main($sz);
        return $sz;
    }
}

var_dump(main($sz));